Toy building block



FIG. 1 is a top plan view of a toy building block showing my new design;

FIG. 2 is a back view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a bottom, plan view thereof; and,

FIG. 6 is a front elevational view thereof. 

The ornamental design for a toy building block, as shown and described. 